I'm kinda stuck on my math homework, does anyone know how to do it?

Question

The results of a blood test at a medical lab are normally distributed with a mean of 60 and a standard deviation of 15. How low must a score be to lie in the lowest 5% of the results?

Answer 1

Look up a normal distribution table for the z-score for 5%. It is approximately -1.65 (you'll have to look it up and refine this value).

This means that all results lower than X=mean - 1.65*σ
= 60-1.65*15
= 35.25 approximately.
will lie within the lowest 5%, if the results are normally distributed.